Process for producing lustrous titanium impregnated yarns



"spinning. luster and transparency of cellulosic materials Patented Aug. 7, 1951 UNITED STATES rnrsNr OFFICE PROCESS FOR PRODUCING LUSTROUS TITANIUM IMPREGNATED YARNS Frederick Roy Millhiser, Richmond, Va., assignor to E, L'du Pont de Nemours & Company, Wilrnington, DeL, a corporation of Delaware No' Drav ving. Application September"18,"1946, Serial N 0. 697,827

7 Claims.

, This invention relates to cellulosic materials of reduced flammability, and more particularly to the production of improved films, fibers, and fabrics of cellulose and its derivatives which are lust'rousyetl contain substantial quantities of'insoluble titanium compounds.

"element which is subsequently precipitated in the'form of one of its insoluble compounds, for egamp1e as an oxide, silicate, phosphate, or

tung'state. Titanium compounds have been found useful for this'purpose but their utility has been limited by attendant, undesired delustering of the impregnated material. This ability of titanium empocnus to deluster is well known and 'it is possible-at times tot'ake advantage of it. Thus,

many'textile materials are delustered by introducing titanium compounds before or after For many purposes, however, the

must be preserved. Brightness and luster are "frequently required in textile materials and to an even greater extent in films and foils. Many "titanium compounds are free from'color, chemically inert, difiicultly soluble, and non-flammable, all of "which make them attractive as flame retarding'agents provided they can be inc orp orated in substantial quantity withoutdelustering the cellulosic material. V Inaccordance with copending application'SerialNo. 69 2,3 86, filed August 22, 1946, lustrous gust 22, 1946, comprises producing a lustrous regenerated cellulosic material of substantially re duced flammability containing at least 3% by weight of titanium, by impregnatin said materailwith "a relatively concentrated solution of a 'wate'r' soluble, inorganic compound of titanium, suchas titanyl sulfate, removing excess impregnant from the treated material by "thoroughly rinsing with an alcohol, and then precipitating a water insoluble titanium compound within the rinsed cellulosic product.

In accordance with one adaptation. of the in- 5 vention disclosed in ccpending application Serial No. 692,386, filed August 22, 1946, regenerated cellulosic yarn or fabric'is suitablyimpregnated by immersion, preferably'in a titanyl sulfate "solution containing from about 50to 'l'50g1ams per liter'of TlQz for a relatively shor'tperiod oft'ime and at room temperature or temperaturesranging from 0 C. to C., care being exercisedn'ot to utilize elevated temperatures at which hydrolysis would occur. Aftersuch impregnation, excess impregnantis removed as thoroughly as possible by conventional hydro-extraction; draining or wringing. These an'd sir'nilar mechanical operations are 'insuflic'ient in themselves, however, to prevent undesired delusterihg of the cellulosic material in the subsequent operatiQnsnecessary to insolubilize or "fix the titanium. When materials treated in this manner are'immersed in aqueous alkali, phosphatesolution, water at ordinary temperature, orother media forfixing the titanium, precipitation occurs on the surface as well as precipitation within the cellulosic material. The cellulosic materialjbecomes coated with a rough, adherent, delustering deposit of titanium compound. This deposit is relatively easy to remove fromfllms but isexceedingly diflicult, if not altogether'impossible to remove from textile materials by mere washing. Seemingly, the deposition is due to incomplete removal of impregnating agent from the surface of the cell.- lulosic material prior to fixation of the titanium as the oxide or otherinsoluble compounds. To overcome this and avoid such deposition, a thorough ringing of ithefimpregnated. material in preferably an alcohol is'resorted to. Ethyl alcohol is particularly preferred, since it does not extract titanyl sulfate from within the fiber yet appears to remove the .titanyl sulfate from the surface of the fiber. The rinsed product can then be Washed with water to insolubilize the titanium sulfate within the, fiber and to, render the yarn sulfate-free, but preferably it is treated with a suitable neutralizing agentsuch as a 3% solution of sodium carbonate, followedby water washing to accomplish the same purpose.

By the process of theinvention described above lustrous, regenerated cellulosic material containing a delustering concentration of a titanium compound may be produced as anew product. The thorough removal of superficialimpregnant, that is, excess titanyl sulfate, is essential to pre vent undesired delustering. The rinsing steps effectively used are rinsing with an alcohol, or aqueous mixtures of an alkali and a polyhydric alcohol or with water at a temperature not above 10 C. While these procedures are effective and useful, more efficient rinsing steps have been sought to permit more economic operation of the process commercially both in respect to time and quantity of materials consumed.

The present invention has as an object the improvement of the production of lustrous, regenerated cellulose material containing a delustering concentration of a titanium compound. A fur ther object is the provision of inexpensive, efficient means for the rinsing of cellulosic material impregnated with soluble titanium compounds. Other objects will appear hereinafter.

These objects are accomplished by rinsing cellulosic materials impregnated with soluble titanium compounds with aqueous solutions of inorganic, neutral salts. r

The following examples, which are merely illustrative and are not to be considered as limitative, are given to provide a clearer understanding of the invention.

Erqmple I Twelve pounds of gel skeins of 150 denier-40 filament Bright yarn were impregnated by immersion at room temperature in a solution of titanyl sulfate for-30 minutes. The titanyl sulfate solution was composed so as to be equivalent to 150 grams of TiOz per liter. The skeins were then washed at room temperature with 10 aqueous solution of sodium sulfate. Washing was effected by the shower method and was continued until the washings were acid free. The skeins were then washed with soft water at room tem perature to remove sodium sulfate. The following steps were then taken in turn at room temperature: a wash using a aqueous solution of sodium carbonate, a soft water wash until the yarn was alkaline-free, a wash using a 3% aqueous solution of phosphoric acid and finally a soft water wash until the yarn was acid free. The treating cycle with the sodium carbonate and phosphoric acid was one hour. The soft water washing treatments were conducted for the length of time required to reach a neutral pH. This generally involved about eight hours. After washing, the yarn Was finished with a solution amount of T102 was 7.9%; the maximum was 12.5 and the average was 9.9

Example II A gel skein of 150 denier-40 filament Bright yarn was immersed in a solution of titanyl sulfate equivalent to 150 grams of TiOz per liter for onehalf hour at room temperature, after which treatment it was allowed to drain for one-half hour in order to remove excess titanyl sulfate. The skein was then washed in sodium chloride solution at room temperature until acid-free. Washing was accomplished by immersing the skein in sodium chloride solution for 5 minutes, and then centrifuging for 2 minutes to remove excess solution and to facilitate the washing operation. The skein was then immersed in fresh sodium chloride solution and the above operation repeated until the skein was acid free. This required seven two-liter washes for a 75 gram skein.

Next the skein was washed with soft water to remove sodium chloride, then with 5% sodium.

carbonate solution, washed alkaline free with soft water, treated with 3% phosphoric acid solution and then washed acid-free with soft water. All treatments were conducted at room temperature. After washing, the skein was finished with a solution of sulfated vegetable oil for one-half hour at C., centrifuged and dried.

TiOz analyses on a skein of Bright yarn treated in the above manner were as follows: minimum amount of T102 was 7.27%; the maximum was 8.26 and the average was 7.77

Although the invention has been described above as applied to certain preferred embodiments thereof, it will be obvious that due variance therefrom may be made without departing from its underlying principles and scope. Thus, although it is particularly applicable to the treatment of textile materials such as cellulosic threads, yarns, or fabrics, the invention is not limited thereto. It may, for example, be applied to films, foils, sheets and even to plastic compositions and molded objects. The materials treated may consist of or contain cellulose acetate or other derivatives of cellulose, for example, cellu lose nitrate, cellulose nitro-acetate, cellulose formate, cellulose propionate, cellulose butyrate, hydroxyethyl cellulose, ethyl cellulose and other esters, ethers, and ester-ether of cellulose. The titanium may be introduced during spinning or casting, as for example by incorporating titanyl sulfate in an acid regenerating bath, or at any suitable stage during subsequent processing or fabrication.

It is usually possible to introduce up to 20% by weight of titanium (calculated as T102) intofilms and up to 13% by Weight into textile materials. The amount of titanium introduced may be relatively small, e. g., as low as 0.5 by weight. At least 3% by weight of titanium is required to materially reduce flammability. The reduction in flammability is directly related to the quantity of titanium introduced and larger quantities (preferably from 5% to 10% by weight). are frequently desirable when the cellulosic material has a large surface area, as in the case of brushed rayon fabrics. Preferably, also, the titanium is precipitated within the cellulose structure as the I oxide, phosphate or phytate.

As noted above, titanyl sulfate is advantageously employed as the preferred impregnating agent by virtue of its high solubility in water, its

It is usually employed in aqueous solutions at a concentration equivalent to, say, from 50 to 150 grams of TiOz per liter, though higher concentrations (up to 200 or 300 grams per liter) can also be used, 1. e., from 5% to 30% TiOz in solution. Excess sulfuric acid above that required for stoichiometric equivalence with titanyl ion sometimes facilitates introduction of the titanium though less than excess is preferred.

The soluble titanium compound may be incorporated in a variety of ways, as for example by a bath treatment, by padding or by spraying. Any soluble titanic, titaneous, or titanyl salt may be used though the sulfates, chlorides, oxalates, and acetates .are particularly suitable. The titanium may be precipitated within the fibers by a variety of agents, for example, phosphates, phytates, silicates, tannates, borates, etc. Though water is preferred as the impregnating and precipitating medium, all or part of the water may be replaced with alcohols, acetone, dioxane, and the like.

It is not, essential to pre-swell the cellulosic structure but this is usually helpful and may be accomplished by soaking in water or other swelling medium or, in the case of regenerated cellulose, by employing so-called gel cellulose which has not been dried after regeneration. The rate of incorporation of titanium may sometimes be increased by raising the temperature of the impregnating solution, but, as already noted, care must be'exercised to avoid hydrolysis. The time of impregnation may vary from a few seconds to a minute or more in case of yarns, fabrics, and films continuously passed through an impregnating bath up to minutes or longer in batchwise impregnations.

The aqueous salt wash may be carried out at any convenient temperature and pressure, though operation at or near room temperature is generally expedient. While sodium sulfate is a preferred agent for use in this step, other water soluble, neutral salts may be used. For example, sodium chloride, potassium chloride or potassium sulfate may be employed with comparable efficiency. So also may the nitrates of lithium, sodium and potassium. In general, any salt which does not precipitate an insoluble titanium compound may be used. These salts may be used in dilute or concentrated solutions. In general, however, concentrations ranging from 5% to are preferred, concentrations of 10% generally being employed.

The temperature of the salt solutions may be varied from 0 C. to 50 0. However, washing of the desired effectiveness is obtained at room temperatures. There is no need to cool the aqueous solutions since the hydrolysis action of the water is sufiiciently retarded by the presence of the salt. Advantages in cost are taken by the operativeness of the wash at room temperature and temperatures in the neighborhood of C. are preferred.

Other advantages attend the process of this invention. Very inexpensive materials are used in the washing step, thereby avoiding the necessity and cost of recovery steps. Further, the amount of Wash material needed to produce the same end condition is materially reduced. For

example, about gallons of alcohol are required to wash each pound of final yarn produced, whereas only 15 to 20 gallons of the less expensive Washing solutions of this invention are re quired per pound of yarn. This means also that the total time consumed in the operatior i of the process is materially reduced. The economic advantages attendant are obvious.

Processing subsequent to rinsing depends upon the particular titanium compound to be precipitated. If titanium oxide is to be precipitated, the especially rinsed materials are simply washed with water until sulfate-free or, since this is slow, neutralized with alkali, preferably 3% aqueous sodium carbonate, and washed with Water. If it is desired to precipitate another insoluble titanium compound, the rinsed material may be immersed in a dilute solution of a compound containing the desired anion, as, for example, a Water solution containing a phosphate, a phytate, or the corresponding free acids. Acids which extract titanium, for example, hydrochloric and sulfuric, should be avoided.

If desired, the process may be used to reduce the flammability of previously delustered materials When it is desirable to avoid further reduction in luster, clarity, or surface deposition of inorganic material.

As many apparently different embodiments of this invention may be made Without departing from the spirit and scope thereof, it is to be understood that I do not limit myself to the specific embodiments thereof except as defined in the appended claims.

I-claim:

1. A process for producing a lustrous regenerated cellulosic product which comprises impreghating a regenerated cellulosic material with a water-solub1e titanium compound; rinsing the resultant impregnated material with an aqueous solution of a water-soluble alkali salt selected from the group consisting of sulfates, nitrates and chlorides to remove superficial impregnant of the soluble titanium compound; and then precipitating a delustering concentration of a waterinsoluble titanium compound ranging from 3% to 20% of titanium by weight Within the rinsed cell-ulosic material by reacting the remaining impregnated soluble titanium compound with a precipitating agent.

2. A process in accordance with claim 1 wherein said salt is a sulfate.

3. A process in accordance with claim 1 wherein said salt is a chloride.

l. A process in accordance with claim 1 Wherein said salt is a nitrate.

5. A process in accordance With claim 1 wherein said salt is sodium sulfate.

6. A process for producing a lustrous regenerated cellulosic product which comprises impregnating a regenerated cellulosic material with a Water-soluble titanium compound; rinsing the resultant impregnated material with a 5% to 20% aqueous solution of sodium sulfate at 0 C. to 50 C. to remove superficial impregnant of the soluble sodium sulfate and the temperature is room temperature.

FREDERICK ROY MILLHISER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,692,372 Gardner Nov. 20, 1928 2,035,483 Kirk et a1 Mar. 31, 1936 2,090,339 Bitter Aug. 17, 1937 2,121,343 Dreyfus June 21, 1938 FOREIGN PATENTS Number Country Date 391,772 Great Britain July 14, 1932 

1. A PROCESS FO RPRODUCING A LUSTROUS REGENERATED CELLULOSIC PRODUCT WHICH COMPRISES IMPREGNATING A REGENERATED CELLULOSIC MATERIAL WITH A WATER-SOLUBLE TITANIUM COMPOUND; RINSING THE RESULTANT IMPREGNATED MATERIAL WITH AN AQUEOUS SOLUTION OF A WATER-SOLUBLE ALKALI SALT SELECTED FROM THE GROUP CONSISTING OF SULFATES, NITRATES AND CHLORIDES TO REMOVE SUPERFICIAL IMPREGNANT OF THE CAHLOIDES TO REMOVE SUPERFICIAL IMPREGNANT CIPITATING A DELUSTERING CONCENTRATION OF A WATERINSOLUBLE TITANIUM COMPOUND RANGING FROM 3% TO 20% OF TITANIUM BY WEIGHT WITHIN THE RINSED CELLULOSIC MATERIAL BY REACTING THE REMAINING IMPREGNATED SOLUBLE TITANIUM COMPOUND WITH A PRECIPITATING AGENT. 